Nonhospitalized Patients With Post-COVID-19 Condition Tolerate Exercise But Show Signs Of Myopathy.

PURPOSE: Many post-COVID-19 patients suffer from persistent fatigue, muscle pain and cognitive problems (termed: post-COVID condition; PCC). Current advice recommends caution with physical activity to avoid worsening symptoms. However, inactivity risks deteriorating health long term. This study aimed to assess symptom exacerbation in PCC patients after exercise compared to controls. Secondly, to explore the physiological mechanisms underlying PCC. METHODS: A prospective, randomized clinical trial, included 31 nonhospitalized patients (46.6 ± 10.0y, 77% women), without concomitant diseases and with persistent (≥3 months) symptoms after COVID-19 infection (PCC group), and 31 age- and sex-matched controls (47.3 ± 8.9y, 74% women). After comprehensive physiological assessment, subjects completed 3 exercise trials (high intensity interval training (HIIT), moderate intensity continuous training (MICT), strength training (ST)). Changes in symptoms from baseline to 48 h post-exercise were compared between groups. Questionnaires, cardiopulmonary exercise testing and physiological characterization provided insights into PCC phenotype. RESULTS: PCC patients had more symptoms than controls at all time points (P < 0.001). No difference observed between the groups in fatigue in either exercise. PCC patients had greater muscle pain change after HIIT compared to controls (P = 0.039). PCC showed concentration difficulties after MICT (P = 0.026). PCC had 20% lower VO2peak compared to controls (29.0 ± 7.6 vs. 35.8 ± 7.7 ml/kg/min P < 0.001). PCC showed preserved lung/heart function but lower muscle strength (150 ± 54 vs.187 ± 64 N·m P = 0.018). PCC spent 43% less time on moderate to vigorous activity (35 ± 28 vs. 61 ± 30 min/day P = 0.001). Of note, 13% of the PCC group had postural orthostatic tachycardia and 62% showed signs of myopathy CONCLUSIONS: Nonhospitalized PCC patients tolerated exercise with preserved cardiovascular function but showed lower aerobic capacity and muscle strength than the control group. They also showed orthostatic intolerance and myopathic signs, suggesting a phenotype linked to inactivity, peripheral tissue damage and neurophysiological changes. Cautious exercise adoption is recommended to prevent further skeletal muscle deconditioning and health impairment in this patient group. The project has received funding via Karolinska Institute from Hannover Re (100,000 SEK), Tornspiran Foundation (50,000 SEK), Lars Hierta Memorial Foundation (42,000 SEK), Magnus Bergvalls Foundation (100,000 SEK) and a grant from CIMED (region Stockholm) of 2,100,000 SEK.